The frequency of the quakes, which continued throughout Sunday night and into Monday, has worried residents and visitors.

Residents and visitors have been advised to avoid large indoor gatherings and areas where rock slides could occur. View on euronews

Schools were closed and emergency crews were deployed on the volcanic Greek island of Santorini on Monday after a spike in seismic activity raised concerns about a potentially powerful earthquake.

Schools remain shut and evacuation flights are underway after Greek holiday island Santorini was shaken by earthquakes for the fourth day in a row. A spike in seismic activity has been recorded on the volcanic island in the Aegean Sea since Friday, sparking fears of a powerful earthquake.

Schools have been closed and emergency crews were deployed on the Greek island of Santorini after a spike in seismic activity raised concerns about a potentially powerful earthquake. Precautions were also ordered on several nearby Aegean Sea islands – all popular summer holiday destinations – after more than 200 undersea earthquakes were recorded in the area over the past three days.

As a result of the heightened seismic activity, schools were closed on the nearby islands and residents on Santorini were advised to avoid large indoor gatherings.

ATHENS (Reuters) -Greek authorities have warned of an increase in seismic activity around the Aegean tourist island of Santorini, advising people to avoid four ports, empty their pools, refrain from gathering in indoor spaces and shut schools on Monday.

The strongest earthquake recorded was magnitude 4.6 at 3:55 p.m. Sunday, at a depth of 14 kilometers (9 miles), the Athens Geodynamic Institute said.

Schools on the Greek island of Santorini have been told to close on Monday in response to an increase in seismic activity in recent days. Authorities have also advised against "large gatherings in enclosed spaces" across the island - a popular tourist destination known for its whitewashed buildings and blue domed churches.

Greek authorities have advised people on the Aegean island of Santorini to shut schools on Monday, avoid two small ports and refrain from gathering in indoor spaces after increased seismic activity in the area over recent days.